The only way to hide a form in CRM 2011 is to remove all security roles from the form. CRM 2013 adds ability to deactivate the form making it unavailable to all users. As expected, form list command bar now has Activate/Deactivate buttons to toggle the status. The buttons are “dumb”, they recognize neither the current form status nor the fact that only forms of type Main can be deactivated, and opt for the error message instead.